Poly(ethylene glycol) (PEG) has been one of the most popular surface coatings for nanoparticles to make them water soluble and not interacting with biomolecules or cells. See, for example, Bentzen, E. L. et al. Bioconjug. Chem. 2005, 16, 1488-1494; and Ballou, B. et al. Bioconjug. Chem. 2004, 15, 79-86, each of which is incorporated by reference in its entirety. However, PEG coatings can add significant hydrodynamic diameter to the nanoparticles, for example when more than 8 units of ethylene glycol are required for water solubilization of the particles. For instance, PEG coatings produce hydrodynamic diameter of greater than 10 nm for an inorganic core/shell of <5 nm. See, for example, Liu, W. et al. J. Am. Chem. Soc. 2008, 130, 1274-1284; and Liu, W. et al. J. Am. Chem. Soc. 2010, 132, 472-483, each of which is incorporated by reference in its entirety. Small hydrodynamic diameter can favor desirable properties, such as to crowded regions for biological studies, efficient Förster Resonance Energy Transfer (FRET), and renal clearance of the particles. See, for example, Howarth, M. et al. Proc Natl Acad Sci USA. 2005, 102, 7583-7588; Groc, L. et al. Nat. Neurosci. 2004, 7, 695-696; Choi, H. S. et al. Nat. Biotech. 2007, 25, 1165-70, each of which is incorporated by reference in its entirety. Identifying more compact ligands has been an issue in the field.